JPH0250817A - Method and device for manufacturing plastic continuum - Google Patents

Abstract

PURPOSE: To manufacture a tape and a film by converting a molten plastic having a relatively high molecular weight to a continuous object, and orienting the object while applying a stress at a specific temperature and a specific orienting speed to quench the object. CONSTITUTION: The plastic is formed of a polyethylene having 400000 to 1500000 G/mol, preferably 500000 to 1200000 G/mol or further preferably 800000 to 1000000 Mw. An extruded material from an extruder 1 is supplied to a cooler 2, and cooled to a melting temperature or lower. The cooled and unoriented extruded material is supplied to a supply roll. Supply rolls have only a roll 4 of a heating roll, heated to 5 to 10 deg.C lower than the melting point of the plastic, then continuously drawn via a furnace 6 by a take-off roll 5. The furnace heats the extruded material to 130 to 160 deg.C. The oriented material is quenched in a stress state between the furnace 6 and the take-off rolls 5, 7. Its orienting speed is 0.1 to 10 sec<-1> or preferably 0.5 to 5 sec<-1> .

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for manufacturing plastic continuous bodies having a shish kebab morphology.

BACKGROUND OF THE INVENTION A filament-like plastic continuum having a shish kebab morphology is disclosed in European Patent Publication No. EPA-151343.
It is known by the number. The continuum morphology is obtained by extruding a polyolefin having a weight average molecular weight of 3×10 5 to 10° g 1 mol in a die approach, applying a temperature several degrees Celsius above the temperature at which the polyolefin spontaneously solidifies.

A disadvantage of the known method is that it is difficult to maintain the temperature within the diamond broach within the required limits, and the production rate of the continuous bodies that can be produced in practice is rather slow. Also, the method is not well suited for film production.

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a method and apparatus for the production of continuous bodies which do not have the above-mentioned disadvantages and which are furthermore suitable for the production of tapes and films. This converts certain types of melt plastics with relatively high weight-average molecular weights (MW) into a continuous article that has a melting temperature (Tm) of unoriented plastics and a higher temperature (Tc). If the stretching speed is higher than the rate of relaxation of the chain molecules under normal conditions (Ve), and the melt exhibits elastic behavior under normal conditions, It is carried out by quenching the stretched product into a continuous body while applying stress at a speed that is not fast enough to begin to show.

European Patent Publication No. EP-A151343 describes extensively what is meant by nunkabab morphology and what conditions are required to obtain high strength. Additionally, Elsevier Applied Science
, London and Nico York
New York), 1987.

Shish kebab morphology exists along the chain and is composed of plate-shaped crystals of bent molecular chains [with overgrowth called kababs J]
It is characterized by a core composed of several elongated polymer molecules called shisi J.

[Plate crystals, also called lamellae J, surround the core and are arranged at angles with respect to the core. In the molded article, the cores are parallel and close to each other, so that the lamellae of one core overlap the lamellae of the other core.

If the melt temperature (Tc) becomes too high, the melt shish kebab that can be formed from the melt of unoriented molecular chains disappears during the drawing process. This temperature was determined for each polymer by means of the molding melting curve known from European Patent Application EP=A-151343. Tissue examination using an electron microscope using a replica is also a suitable method.

The stretching temperature should not exceed the temperature Tc found in this way.

Special attention should also be paid to the drawing speed.

Here, the stretching speed is the stretching ratio (lambda) divided by the time (seconds) required for stretching. Here, the stretching speed (lambda) is the ratio L/Lo (Lo is the initial length, ■ is the length after stretching). Two contradictory phenomena occur during stretching. As the molecular chains are stretched under the influence of the stretching force, they are aligned parallel to the direction of the stretching force;
This phenomenon is caused by the so-called relaxation, which tends to return the molecular chains to a coiled, disordered state.
ion). Since the relaxation proceeds at a certain speed, the stretching speed must be faster than the relaxation speed. The point at which these speeds cancel each other out as they are and the corresponding drawing speeds can be easily determined empirically: i.e., for polymers with low Mw, the solid is faster than the liquid; It's also fast.

The stretching speed should not be too high. This is because otherwise the melt would react elastically and break. Thus, the drawing speed can be easily determined empirically.

In order to achieve higher than usual E modicolus and tensile strength, the weight average molecular weight MW should be selected within appropriate limits. If Mw is too small, the lamellae do not overlap each other because either no shin-kebab morphology is formed in the melt, or because the non-to-kabab ratio is too small or the cores are too far apart. On the contrary, M
If w is too large, problems will occur during processing, for example in an extruder. Here, those skilled in the art use empirical advice.

From a technical standpoint, using polymers with a broad molecular weight distribution increases the chance that the stretching speed and the stretching speed will cancel each other out.

This is because such polymers have a broad relaxation spectrum.

The polymer in the part always takes a non-form.

By quenching, the resulting sinker-pab morphology in the stretched volume is frozen under stress, and the stretched volume is formed as a film or filament with high E-monulus and high tensile strength.

The invention is particularly applicable to copolyolefins, such as several homopolymers, copolymers or copolymers of two or more.

Due to its simple molecular structure, Plusdec preferably has a molecular weight of 400,000 to I, 500,000 g per mol, preferably 500,000 to 1.200 000 g per mol,
More preferably, it is made of polyethylene having a Mw of 800,000 to 1ooo, ooo.

Polyethylene herein includes copolymers of ethylene containing at most 3% by weight of alkenes-I having 3 or more carbon atoms.

For polyethylene with Mw of 400.000 to 1,000,000 g 1 mol, the stretching temperature is preferably 13
The temperature is 0 to 160°C, particularly preferably 140 to 160°C. For other polymers, these limits can vary. In the case of polyethylene having a Mw of 400,000-1,000,000 g/mol, the stretching speed is preferably 0.1-10 sec=, more preferably 0,5-
55ec-'.

The invention also relates to an apparatus for carrying out the invention, consisting of an extruder and a downstream drawing device consisting of at least a feed roll, a take-off roll and a heating furnace therebetween. The apparatus includes a cooling device disposed between the extruder and the feed roll for cooling the extrudate to a temperature between the extrusion temperature and the melting temperature of the plastic, one or more of the feed rolls being a heating roll; It is characterized by the provision of means between the heating furnace and the Yumitori roll to rapidly cool the stretched body.

With well designed equipment it is possible to control the temperature of the extrudate during drawing. By controlling the temperature in the cooling device according to the extrusion temperature, the stretching process can no longer be carried out regardless of the temperature of the extrusion process.

The cooling device can be controlled by liquid or gas.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

EXAMPLES A number of polyethylene grades were used in the tests as shown in Table 1 along with their Mw, Mn (number average molecular weight) and Mw/Mw ratios and their manufacturers.

Samples of polyethylene reactant powder with a thickness of 0.5 mm were prepared by compression molding for 15 minutes at a temperature of +4.5 °C, followed by quenching in cold water. A test piece was cut from the sample, stretched to a maximum temperature above the melting temperature at a stretching speed of 5 sec-', and then cooled under stress.

The tensile monoculus was measured on a test piece with a length of 10 cm at a speed of 1 mm/min using an Instron tensile tester. The cross-sectional area was calculated from the weight of the test piece based on a polyethylene density of 0.97.

Table 2 shows the stretching temperature, stretching ratio, and strength properties measured for each polyethylene in Table 1.

As is clear from Tables 1 and 2, Mw400.
If it was less than 000, good mechanical properties could not be obtained even at a high draw ratio. Not only is it difficult to process polyethylene above Mwl, 00o, ooo, but none of the mechanical properties obtained are surprisingly interesting. The tensile strength of Hizex 2420 M was only 0J5GPa.

FIG. 1 is a schematic representation of an apparatus according to the invention, with which the method according to the invention can be carried out. The extrudate in filament, tape or film form from the extruder (1) is fed to a cooling device (
2) where the extrudate is cooled below its melting temperature. The cooled, unoriented extrudate from the chill roll is fed to a feed roll section, which feed roll has e.g.
The supply roll (4) is the only heated roll and is heated to 5-10° C. below the melting point of the plastic and is then continuously withdrawn through the furnace (6) by a take-off roll (5). The furnace heats the extrudate to a temperature of 130-160°C. Since the take-up roll (5) has a faster circumferential speed than the roll (4), stretching occurs in the furnace. Rolls (3) and (4) have the same circumferential speed. A cooling device (2) and a heated feed roll (4) control the extrudate to be drawn at a good temperature in the furnace. Heating furnace (6) and take-up roll (5)
, (7) schematically shows means for rapidly cooling the stretched body under conditions of stress.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the apparatus of the invention. The main symbols in the drawings have the following meanings. 1. Extruder, 2. Cooling device, 4. Supply roll, 5. Take-up roll, 6. Heating furnace.

Claims (10)

[Claims] (1) Converting a melt plastic with a relatively high weight-average molecular weight (Mw) into a continuous product, which has a melting temperature (Tm) of the unoriented plastic and a higher temperature (Tm).
c) at a temperature between
characterized in that the drawn product is quenched into a continuum under stress at a rate between e) and higher, but not so high that the melt begins to exhibit elastic behavior under normal conditions. A method for producing a plastic continuum having a shish kebab shape. (2) The method of claim 1, wherein the plastic is polyethylene having a Mw of 400,000 to 1,500,000 g/mol. (3) The method of claim 1, wherein the plastic is polyethylene having a Mw of 500,000 to 1,200,000 g/mol. (4) The method according to claim 1, wherein the plastic is polyethylene having a Mw of 800,000 to 1,000,000 g/mol. (5) Claim in which the stretching is carried out at a temperature of 130°C to 160°C (
The method according to any one of 1) to (4). (6) The method according to any one of claims (1) to (5), wherein the stretching speed is 0.1 to 10 seconds^-^1. (7) The method according to any one of claims (1) to (6), wherein the stretching speed is 0.5 to 5 seconds^-^1. (8) Consisting of an extruder and a downstream stretching device consisting of at least a supply roll, a take-up roll, and a heating furnace disposed therebetween, with a cooling device disposed between the extruder and one or more supply rolls, and one of the the supply roll is a heating roll;
8. The apparatus according to claim 1, further comprising means for rapid cooling between the heating furnace and the take-up roll. (9) The method and apparatus described and/or illustrated in the drawings. (10) A plastic continuous body produced according to any one of claims (1) to (9).